Telephone system.



H. G. WEBSTER. TELEPHONE SYSTEM.

APPLICATION FILED MAE. 7, 1903.

Patented Feb. 15,1910.

it included between said windings. This artral oflice.

,central oflicethe cut-oft spond. In such prior systems, however, the

two

UNITED A'gtgg PATENT orri'cn fl.

OF CHICAGO, ILLINOIS,

I TELEPHONE SYSTEM.

Specification of Letters Patent. l pplicati on filed March 7, 1903.

949,012. Patented Feb; 15, 1910.

Serial No. 146,622.

To all whom 'it may concern:

Be it known that I, HARRY G. WEBSTER, a citizen ofthc United States of America, and residing at Chicago, in the county of Cook and-State of Illinois, have invented a certain new and useful Improvement in Telephone Systems, of which the following is'a speci l fication. T My invention relates to telephone systems, myobject being to provide means in the line circuit and in the cord circuit whereby certain'new and useful results are accomplished. It has been sought heretofore to provide telephone circuits with differential cut-01f indicate subscribers lines extending in tWo l mbs 2 and 3 from their respective substatlons A-and C to the central oflice. At the latter they are each provided with a calling signal S, preferagly in the form of aismall incandescent lamp, and with a plurality of connection terminals or spring jacks J, J 2 and J. The line conductor 2 includes the winding of the line relay R and the differential windings 4 and 5 of the cut-off relay R and is thence connected hv conductor 6 with the grounded battery B. The line relay controls through its normally open contacts circuit ofthe signal S, while the cut-ofi' relay" R controls through its normally open contacts a shunt of line relay R and of the winding 4 of itself, said shunt consisting of the branch conductor 7, the spring 8 of the cut-off relay R and the branch 9 connected With-the conjunction point 10 of said two differential windings 4 and 5 of the cutofl" relay.. The point 10 is ll with the tip contacts two windings of the-cut-ofi" relays have been placed in the opposite sides of the line, circuit and the battery atthe central office is rangement has the disadvantage that the line circuit must be maintained in a balanced condition or thecurrent flowing through the of the several jacks, permanently connected by conductor 12 with the line conductor 3. The latter conductor is connected by a lead 13 with the live pole of said battery B and includes a retardation coil 14. Y

The central oHice equipmentincludes the cord circuit having an answering plug P and a'calling plug P provided with tip and sleeve contacts adapted to register respectively with the corresponding contacts s of the jacks when the plugs are inserted therein. The tip contacts of said plugs are connected bymeans of flexible strands t and t the cut-off relay and the same will be undesirably actuated. V

y invention seeks to avoid this difficulty and one method for accomplishing the desired result consists in placing the cut-0H relay wholly in one line conductor so that whether the line is balanced or not, the current flowing through its two coils always I produces equal and opposite etfects therein so that under all conditions of use the said relay does not respond to the current in the line when the subscriber is calling the cen- 40 Another feature ofthe invention resides and the interposed condenser 0, while the in the novel cord circuit which lSlIlQle parsleevecontacts are joined by similarv strands ticularly designed to coiiperate with-the line 8 and s and the vinterposed condenser 0 circuit or circuits shown al'iddescribed. Supervisory relays "r 'and r? are bridged The invention is illustratediin the accomacross the answering end of the cord circuit panying t'lrawings in whielrthe same referand control through their contacts the local encc characters are used throughout thesevcircuit of the supervisory lamp or other eral figures to designate like parts and insignal S associated with the answering plug which t P, tliewontacts, of the fornier relay being Figure l is a diagram of the system-[emu normally open and those of "the latter relay ,50 bodying my improven'ients; Fig! 2 is a sims. being normally closed. An intermediate plified diagram of the line circuits, and F point the bri-dge of said relays is joined 3 isa simplified diagram of a modified formi "y conductors 15, and 16 with t e live pole of t e line circuit. iof"battery.B. A second supervisory lamp 1 Referring particularly to Fig. l, L and L pole of a central common the local joined by conductor across the calling end of t S is associated with the callin plug P and has its local circuit controlle n a mannerdium of any suitable listening key, her transmitter 20 and the primal}; of her induction coil 19 being charged r source and which maybe the said battery B. A suitable rin 'ng generator 21 is adapted to beconnecte between ground and the sleeve strand of the. cord circuit by means of the sleeve spring 22 of any suitable ringing key, while the t1 strand is, simultaneously connected throng the spring of said key with the conductor 23 containing a resist! ance coil 24 and leading to the conductor 13 and thence to the battery B.

' At the substation a bell 25 and condenser c are included in a permanent bridge of the line conductors, while the transmitter 26 and receiver 27 are adapted to be included in a bridge of said line conductors,whose normal. discontinuity is maintained. by the switch hook 28. This apparatus'is intnded merely to typify any usualor desired common bat 'tei y substation a paratus;

= he line relay may have a resistance of 100 ohms. and the windings 4 and 5 of the I cut-olf relay R may each be of 100, ohms crating supervisory relays r and 1" ma e,

resistance. 1 The retardation coil 14 may have 500 oh'ms resistance, the supervisory relays r and '1' 500 ohms eachTfid the e06 of 100 ohms each. For the pur ose 0 accomplishing the busy test retar ation, coils 29 may be bridged across each end ofthe' I cord circuit and may be from 2000 to 4000 ohms resistance. It will be understood thatv I th'ese' resistances are not meant to be arbi-' trary and may be varied to any suitable de ree.

a n the operation of the 'system, the sub; scriber A for example takes up his receLver and completes a path for current over the.

metallic nefrom the battery B. This current flows serially through the two windings 4 and 5 of the cut-oli'reluyR, which does not respond and thence through the line refor current t lay R which is actuated to closethe local circuit of the'line signal S; Upon observing.

this si nal the operator inserts the answering plug 1 of her'cord circuit and connects her telephone in the cord circuit to receive the order from the subscriber. The insertion of the answeringplug P completes a local path roughthe winding 5 of said om any suitable relay R over' conductor 6, through winding 5, conductor 11, tip strand t, supervisory relay 'r, conductor15 and conductor. 16 to the live pole of said battery. The current in this path is suflicient to unbalance the magnetism 10 of relay- R which is actuated and closes a shunt about the line relay R which is de energized and rendered inoperative throughout the remainder of the connection. The current in this path is also suificient to actuate the supervisory relay 7, thus closing the I local circuit of supervisory lamp 8, but said I lamp does notlight' owing to the fact that. the supervisory relay 1* is also energized by currentfrom said source flowingjover the so teleFhoneJine tothe substation and in pare. 'alle through the branches 12 and. 13 to the. live pole of. said battery B, that in the branch l2 and over the sleeve strands of the cord, I circuit being sufiicient to operate the relay 7!. The supervisory lamp S therefore remains inert. U pon learning the subscriber wanted the condition of 'thatline is testedin the usual way by touching the tip of the calling I plug to t e test ring ofthe multiple jack of the line that is located upon the operatorsf section. It will be observedthat normally" the sleeves or test rings, of the jacks are connected to the live pole of battery B and since, the tip of the plug is likewise connected '95 through the supervisory relay 1' andconductors 17. and 1'6 with the live pole of said battery, no flow of current takes place when an idle line is tested and the o crator knows nection is established at some other section of the switchboard, a cord circuit of the type shown in the drawingisinserted in one of. the jacks of the line, and a flow of current is taking placefrom the live pole of the-battery 102"; B over conductor 16, through either su ervisory relay 7* or r to the correspo'n ing sleevestrand s or 8 and thence through the lettlldtttlOllCOlT 29 bridged across that end of the cord circuit and thence over the propertip strand of theinserted cord circuit over I tip conductor 11 of the jacks of the line, and thence through the winding 5 of the cut-ofl? relay and over'conductor 6 to ground- This the live pole 'of the battery at thesleeve,

Since he sleeve contact of said-inserted lug and therefore the test rings of the packs strand sore, said test rings are also at a I r lower potential th n that of the livepole of Ithe battery B. hen, therefore, the tip of the testing cordcircuit is brought into conrent results and a-click. is received by the testing operator, who then knows that thef line'is busy. I t Upon finding a 3 .the line idle the'calling lug P? is inserted in the jack of the-line and thatthe line is not busy. If, owever, con- 109- results in a fall of potential with'respect tollh strand 8 or .9 of the inserted c'ord circuit and I are at the same potentialas the said sleeve 9 tact with one of said test'rin'gs, a flow of CH1", 1.25"

the

ringing key 22 operated.

the calling plug results in ing 5 of the cut-ofi' relay local circuit; whichactuates slaidf1 fly. to completely shunt about the line relayfltand thus to prevent its operation. The actuation closing the windof the ringing key does not alterjthis condi tion for although the tip strand t is severed,

an auxiliary path, for current thereover' is provided through the tip spring 22 of said key and over conductor 23 to the live pole of-said battery B. The ringing current passes out overthe sleeve conductor of the cord circuit and'line toth'e'substation and back to the central oflice, through the shunt of the line relay and winding 4 ofthe cutofi' relay, and thence over the tip conductor 11, t1p strandt conductor 23 containing actuated to close the circuit of supervisory .lam'p S which is now lighted owing to the fact that the sleeve supervisory relay 1 is not yet operated. Upon the subscribers response said latter relay receives current over the metallic line and is actuated to open its normally closed contacts to render said lam inert. The subscriber-s are now in communlcation and the'battery Bis feeding current out over the telephone lines'for transmission purposes. Tracing the path for this current from the positive pole of said battery B, it flows out over conductor 6 through winding 5 of-sa-id relay and thence shunt of the winding 4 of said relay and of the line relay R, thence over line conductor 2 and through the substation devices, back to the central oflice over line conductor 3 where it divides between the branches 12 and 13, a greater portion flowing through the branch -12 owing to the low resistance of the -supervisory relay 1' as compared with the retardation coil 14. The return current thus reaches the live'pole of battery B. The path through the tip strand of the cord circuit and supervisory relay 1' is, as is apparent, in parallel with the line circuit, but owing to the high resistance of said relay the line circurrents thus" pass directly from the conductor 11 to the line conductor 2 over the shunt of said Winding 4 and the relay R and thus sufi'er no impedance therefrom. The

resistance of these windings and the line relays are also removed from the talking circuit. During conversation the retardation coils 29 prevent the passage of the voice currents'across the cord circuit.

Fig. 2 illustrates the same line circuit as Fig, 1, but in' a simplified form. With this The insertion of of saidline ina; w A 4 are'plac it uit i 'h controlled 7 through through the circuit, the t1p contact mon return may be used for the subscribers lines sincebothgthe line and cut-oil rela 's the same side of the battery in I L M inefconductors.

" ltig fishowsgan arrangement of line cirhorm'ally closed contacts of the c'ut-ofl' relay R and the normally open contacts of the line any R, the latter being placed upon theoth 1' SlCle of the battery B and taking theplace 14 in the other figures. 1 vided with a shunt of its prior circuits but said shunt does not include the line relay. The operation in connection Said relay is pro with this figure is thought to 'be obvious.

The relay Rre'sponds to the calling current in the line when the subscriber is a central office, and the cut-0H relay B" does not respond. I The lamp r eratoranswers the call the cut- S is thus lighted. When theo oli relay R is unbalanced as before described render the same inert. At the same time the winding 4 of said cut-01f relay Rfiis shunted its resistance and retardation from to remove the line circuit. Theresistance 0f,'Sfl1d line relay R would, in this instance be 500 ohms,

. nect therewith, a source of current,.one pole of said source being connected withthe sleeires of said multiple jacks and tip and sleeve strands of the cord circuit, the tip contacts of the oh the line signal S has its circuit and the local circuit of lamp S is opened to thecombination 105 v multiple jacks being con-. 'nected with the other pole of said source, and

farrangemeut it will be observed ,that a comof the retardation-coil winding 4 as in the a calling the the operationis with the an impedance conneizted between the tip and sleeve strands of the cord-circuit to establish a change of potential of the sleeve contacts of the jacks when the cord is connected with one of said jacks, whereby the busy condition of the jacks may be ascertained from the condition of the test contacts of the, multiple jacks in the various positions, substantially as described.

2. In a telephone system, the combination with a telephone line, of a cord circuit to connect therewith, a source of current, one pole of said source being permanently connected with the sleeve of the line jack and with the'tip and sleeve strands of the cord of the line jack being permanently connected with the other pole of the source, and a path for current between the tip and sleeve strands of the cord circuit to establish a change of potential of the sleeve contact of the jack. when the cord is connected With the line, whereby the busy condition oi the line may be ascertained b connecting with the test contacts of the mu {-Itiple jacks, substantially as described. In a telephone system, the combination with a source of current, of multiple jacks having their sleeve contacts permanently connected-F with a pole of said source,,a cord ple "acks, the potential of the sleeve contacts bf t e jacks will be changed to indicate the busy condition of said jacks, substantially as described.

withla telephone line, of a cord circuit to connect therewith, a'source of current having one pole permanently connected with the sleeves of the line jacks and with the tip and sleeve strands of the cord circuit, and the other pole connected with the ti of the line jacks, and a high resistance and impedance connected in a bridge between the ti and sleeve strands of the cord circuit, su tantiallyias described. J"

Signedb me at Chica o, ccunty'of Cook, State of II inois,this 26t day of February v HARRY G. WEBSTER. Witnesses: j ROBERT Lnwrs Arms,

GAZELLE BEBE-R. 

